Abstract

A new method for quantifying the total ozone column (TOC) using a smartphone image sensor has been developed and validated. The TOC has been evaluated for relatively cloud free days at high air masses for solar zenith angles between 49.7o and 76.7o at a sub-tropical site. The method is based on the evaluation of the direct solar irradiances at 305 nm and 312 nm using the red colour pixel values of the solar disc recorded at these wavelengths by a smartphone camera. Narrow bandpass filters of 2 nm FWHM at each of the two wavelengths were used in turn placed over the camera sensor to directly image the solar disc. The calibration of the pixel values of the solar disc to provide the direct solar irradiances at each of these two wavelengths allowed evaluation of the total ozone column calibrated to a portable sun photometer. The RMSE for the smartphone derived ozone values calibrated to corresponding values from a portable sun photometer was 4.3 DU. The validation measurements for the smartphone derived ozone values provided an average residual of 3.5% (up to a maximum of 11%) compared to the corresponding portable sun photometer values, with an RMSE of 8.4 DU during days of intermittent inclement weather conditions. The evaluation of the total ozone column based on a widely available device such as a smartphone has the potential to increase current citizen science initiatives valued by the general public and school aged learners by enhancing knowledge and awareness of ozone and the resulting influences on the solar UV environment.